Site Coordination Team

Technical Advisory Panel

News and Results

August 3rd, 2011 Construction of our test specimen began on July 27th, 2011 and finished on August 1st, 2011. A time-lapse video on the images page
shows the construction sequence, which spanned four days. John Lemke from GeoDaq helped set up a data acquisition system to remotely record
pore pressure and settlement during consolidation of the embankment. The data can be viewed at http://geodaq.com/servlet/login1 using username: ucla and
password: geodaq. Doug Wahl, a UC Davis graduate student, helped us conduct a cone penetration test with shear wave velocity and pore pressure measurements using the nees@UCLA CPT rig.
The peat thickness is approximately 11m at our site. We are processing the CPT data and will make it available in the NEES data repository soon.

June 15th, 2011 A team of five researchers from UCLA and Cal Poly performed a hand auger site investigation on Sherman Island at our site location.
The upper 1.5m of peat above the water table was unsaturated and fairly strong, whereas the saturated peat below 1.5m was very soft. Vane shear measurements indicated that the
peak undrained shear strength ranged from about 10 to 20 kPa in the saturated peat, with residual undrained strengths around half of the peak. The peat is so
soft and weak that a 75mm (3") diameter hand auger could be
monotonically pushed vertically ....

Project Summary

The Sacramento-San Joaquin Delta levees are critical components of California’s water
distribution system. The Delta supplies fresh water to over 22 million people in southern
and central California as well as eastern portions of the bay area and directly supports
California's $400 billion/year economy. The “islands” circumscribed by the network of levees
are commonly 3 to 5 meters below sea level, and are protected by only about 1 to 1.5 meters
of freeboard at high tide. A breach in a levee causes water from the channel to flow into
the island thereby inundating farmland and wildlife habitat, and
potentially locally reversing the direction of flow in the
channels thereby drawing saline water into the Delta from the
west. Simultaneous inundation of multiple islands, as
predicted for a moderate earthquake in the region, could degrade
water quality to the point that delivery would be halted. Delta risk
assessment has recently gained a significantly enhanced priority in the wake of (1)
an unexplained breach of Jones Tract in the Delta in 2004, causing over $100 million in losses
and (2) the catastrophic levee failures in New Orleans following hurricane Katrina. The risk
posed to the Delta by a strong earthquake is particularly onerous due to the potential for
widespread simultaneous levee failures that would overwhelm a disaster recover system that
often struggles to rapidly repair a single breached levee. The influence of earthquake shaking
on the behavior of the levees is uncertain because the cyclic deformation potential of the
underlying peaty organic soils not well understood, and there is an urgent need to investigate
the behavior of these materials to clarify likely failure mechanisms.

This project will involve full-scale testing of an existing
levee or earth embankment to investigate the in situ deformation
potential of peaty organic foundation soils under realistic stresses and boundary conditions.
The test conditions and instrumentation will be designed to measure the deformation
mechanisms that can result in a critical loss of freeboard leading to a breach. Data of this
sort is essential for the development of more rational (and meaningful) analysis tools for
assessing the seismic vulnerability of levees. The field testing will be supplemented by an
extensive laboratory testing program to further investigate key material response characteristics
such as cyclic pore pressure generation and its effects on shear strength and post-cyclic
reconsolidation. The improved knowledge of levee seismic vulnerability will be broadly applicable
wherever these earth structures are founded on organic soils. The proposed testing activities
are being closely coordinated with stakeholders and
environmental regulators at potential test sites in the Delta
and Suisun Marsh.